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Lecture Comments (5)

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Post by dzung tran on April 9, 2014

Tell me if I'm wrong but I think that the first Example is done wrongly. 23/20 simplified would not equal 20 1/3(which is actually 60/1).Rather it would equal 1 3/20.



:D

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Post by Valdo Ribeiro on December 14, 2011

Great lesson,thank you.

1 answer

Last reply by: Justin Francisco
Thu Sep 4, 2014 8:48 PM

Post by Valdo Ribeiro on December 14, 2011

3/4+2/5=23/20= 1 3/20 (clockwise)

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Post by Danno Allgrove on September 30, 2010

Nancy, on Extra Example III, you mistakenly used 2 and 1/4 for the first number instead of the 12 1/4 shown in the problem. You just happened to not have double-checked your answer on this one or you would have caught it. :)

Adding Rational Numbers

  • To add fractions with unlike denominators write equivalent fractions with a like denominator. Then add the numerators, keeping the denominator the same. Remember to simplify!
  • Any common denominator may be used. You can multiply the denominators of two fractions to find a common denominator. However, using the Least Common Denominator (LCD) may save steps and make it easier to simplify the final answer.
  • To add rational numbers you can change all numbers to decimals or all numbers to fractions.

Adding Rational Numbers

[1/4] + [3/5] =
  • [5/20] + [12/20]
[17/20]
− [2/3] + [5/7] =
  • − [14/21] + [15/21] =
[1/21]
[3/8] + [5/12] =
  • [9/24] + [10/24] =
[19/84]
− [3/10] + [8/15] =
  • − [9/30] + [16/30] =
[7/30]
Change to fractions to solve. 3.25 + [3/4] =
  • 3[25/100] + [3/4] =
  • 3[1/4] + [3/4] =
  • 3[4/4] =
4
Change to fractions to solve. − 1.2 + 2[17/20] =
  • − 1[2/10] + 2[17/20] =
  • − 1[4/20] + 2[17/20] =
1[13/20]
Change to decimals to solve. 3[3/5] + 2.7 =
  • 3[6/10] + 2.7 =
  • 3.6 + 2.7 =
6.3
Change to decimals to solve. − 1.7 + 5[7/20] =
  • − 1.7 + 5 + 20|  5.00   =
  • − 1.7 + 5.35 =
3.65
Change to fractions to solve. 4[7/30] + 1.8 =
  • 4[7/30] + 1[8/10] =
  • 4[7/30] + 1[24/30] =
  • 5[31/30] =
6[1/30]
Change to fractions to solve. − 2.3 + 1[1/8] =
  • − 2[3/10] + 1[1/8] =
  • − 2[12/40] + 1[5/40] =
− 1[7/40]
A recipe calls for 2[2/5] cups of sugar, 3[9/10] cups of flour, and 1[4/15] cups of chocolate chips. How many cups of materials does the recipe need?
  • 2[2/5] + 3[9/10] + 1[4/15] =
  • 2[12/30] + 3[27/30] + 1[8/30] =
  • 6[47/30] =
7[17/30] cups

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

Adding Rational Numbers

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • What You'll Learn and Why 0:05
    • Topics Overview
  • Vocabulary 0:19
    • Least Common Multiple (LCM)
    • Least Common Denominator (LCD)
  • Adding Fractions with Unlike Denominators 1:22
    • Example: 3/4 + 2/5
    • Example: -3/5 + 1/7
  • Adding Different Forms of Rational Numbers 3:23
    • Example: Change to Fractions
    • Example: Change to Decimals
  • Extra Example 1: Adding Different Forms of Numbers 7:02
  • Extra Example 2: Exercising 10:06
  • Extra Example 3: Adding Different Forms of Numbers 11:20
  • Extra Example 4: Cooking Recipe 13:47